A synthetic resin is widely used as a material for construction of buildings, electrical machinery and devices, automobiles and fibers because it is generally light, excellent in water and chemical resistance, has excellent electrical insulating and mechanical properties, and is easy to mold. However, a synthetic resin has the drawback that it is more flammable than a metallic or inorganic material. Consequently, various methods for imparting flame retardance to a synthetic resin have been proposed. Of these, a method of incorporating a halogen compound, a phosphorus compound, an inorganic hydrate and the like into the synthetic resin is most widely used. Particularly, an organic phosphoric acid ester compound such as triphenyl phosphate, cresyl diphenyl phosphate, or tricresyl phosphate is widely used industrially. However, conventionally used flame retardant agents have drawbacks in causing smoking and volatilizing during the molding processing, bleeding to the surface of moldings and the like.
In order to alleviate the above drawbacks in practice, it has been attempted to use a phosphoric acid ester compound having high molecular weight as a flame retardant agent. For example, European Patent Unexamined Publication No. 7,460 discloses a tri(2,6-dimethylphenyl)phosphate compound; European Patent Unexamined Publication Nos. 129,824, 129,825 and 135,726 and British Patent Unexamined Publication No. 2,043,083 disclose a resorcinol-bisdiphenyl phosphate compound and the like; and U.S. Pat. No. 4,683,255 discloses a tribiphenyl phosphate compound. However, large amounts of these phosphoric acid ester compounds must be used in order to impart flame retardance to the resin. Further, according to our research findings, these phosphoric acid ester compounds do not satisfy recently established standards because they cause corrosion during molding, they are denatured during molding or during prolonged use of the moldings, and cause the moldings to discolor, blister and deteriorate in electrical properties and flame retardance due to water absorption and the like.
Thus, the art has not been able to provide a resin composition possessing both sufficient flame retardance and performance as a product.